Many rubber articles, principally automobile tires, hoses, belts and the like are known as composites and are reinforced with fibers or wires. In all such instances, the fiber or wire must be firmly bonded to the rubber.
A frequent problem in making a rubber composite is maintaining good adhesion between the rubber and the reinforcement. A conventional method in promoting the adhesion between the rubber and the reinforcement is to pretreat the reinforcing fiber with a mixture of a rubber latex and a phenol-formaldehyde condensation product wherein the phenol is almost always resorcinol. This is the so-called "RFL" (resorcinol- formaldehyde-latex) method. An alternative method of promoting such adhesion is to generate the resin in-situ (in the vulcanized rubber/textile matrix) by compounding a phenol-formaldehyde condensation product (hereinafter referred to as the "in-situ method"). The components of the condensation product consist of a methylene acceptor and a methylene donor. The most common methylene donors include N-(substituted oxymethyl) melamine, hexamethylene tetramine or hexamethoxy methyl melamine. A common methylene acceptor is a dihydroxy benzene compound such as resorcinol. The in-situ method has been found to be fairly effective where the reinforcing material is steel wire since pretreatment of the wire with the RFL system has been observed as being largely ineffective. Unfortunately, the products using the in-situ method has still fallen short of the demands of the consumer.
The purpose of the present invention is to further improve the adhesion between the fiber or wire reinforcement and its rubber environment to satisfy this shortcoming in the existing technology.